A conventional grill device generally has two shells, a hinge pivotably interconnecting the shells to allow relative folding and unfolding movements with respect to each other, and two grill plates respectively mounted on the shells. For grilling a variety of food, one of the shells is made to accommodate grill plates of different depths. However, when it is desired to use a deep grill plate that has a higher peripheral rim projecting from the shell with a larger height, the shells cannot be successfully superimposed upon each other when folded.
Referring to FIGS. 1 and 2, a conventional grill device 1 includes a lower grill unit 11, an upper grill unit 12, and two hinge mechanisms 13 (only one is shown) respectively disposed at left and right sides of the grill device 1 and pivotably connecting the upper grill unit 12 with the lower grill unit 11. Each of the hinge mechanisms 13 is in the form of a linkage mechanism, and includes lower and upper shafts 131, 132 which are respectively connected to the lower and upper grill units 11, 12 and which are linked to each other by pins 133, such that the upper grill unit 12 is moved to permit an upper grill plate 121 of the upper grill unit 12 to be superimposed upon a lower grill plate 111 of the lower grill unit 11 when the grill device 1 is closed. The lower and upper shafts 131, 132 are respectively formed with front positioning surfaces 134, 136 that abut against each other when the upper grill plate 121 is stacked upon the lower grill plate 111 of a smaller height, and are respectively formed with rear positioning surfaces 135, 137 that abut against each other when the grill device 1 is opened. However, the hinge mechanism 13 is liable to sway when a lower grill plate 111 of a larger height is employed and there is no positioning structure for positioning the hinge mechanism 13 in a closed position of the grill device 1, which renders use of the grill device 1 unstable and unsafe. Moreover, the hinge mechanism 13 is bulky and is exposed at two sides of the grill device 1, which adversely affect the outer appearance of the grill device 1.